The present embodiments relate to mip-map construction for volume rendering, such as texture-based volume rendering. Mip-maps are created at different resolutions. A series of down-sampled volumes are created from an initial volume. For rendering, the map whose projections best match the screen resolution is used. The principle is to make one voxel project to approximately one pixel. This reduces aliasing artifacts and may also improve rendering speed.
For creating each mip-map, each dimension of a texture is down-sampled by a factor of two to create the next level of texture (e.g., 16×16×16 to 8×8×8). One type of mip-map is a rip-map where down sampling along one or more dimensions is by a greater amount than other dimensions, but still at a power of two (e.g., 16×16×16 to 8×8×4). Down sampling by a power of two facilitates the interpolation between adjacent mip-map levels for rendering. In texture-based volume rendering, it may be computationally expensive to involve more than one mip-map level in one rendering pass.
Some volume datasets are anisotropic. The voxel sizes and/or number of voxels along the three major axes are different. Each voxel and/or the volume may not be in the shape of cube. For example, the voxel size in Z is only ¼ of that in X or in Y, where X, Y, and Z are the major axes. Down sampling by a power of two may result in a similarly anisotropic mip-map level.